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Study Finds Sleep Disturbances in Parkinson’s May Be Related to Circadian System Dysfunction

- Apr 25 2014

Irregularities in the rhythms of the body’s biological clock may play an important role in the sleep disturbances associated with Parkinson’s disease (PD). This finding, which appears in the February 24 online edition of JAMA Neurology, is among the first to shed light on this poorly-understood issue experienced by people with Parkinson’s disease.

Sleep disturbances are a major challenge for many people with Parkinson’s disease. In fact, close to 90 percent of people with the disease have trouble getting a good night’s sleep. Lack of sleep can cause excessive daytime sleepiness (EDS), which can seriously impact quality of life and lead to health problems. Yet because scientists do not yet understand why sleep disturbances occur in PD, there are few effective treatments available.

Changes in circadian rhythms – which are changes in the behavioral, biochemical and physiological processes that control our biological clock – have already been linked to sleep disorders in the general population. Aleksandar Videnovic, M.D., M.Sc., Massachusetts General Hospital, has been studying their relationship to PD, in part with funding from a three-year PDF/American Brain Foundation (ABF) Clinician-Scientist Award. In particular, he and colleagues from Northwestern University and Lund University in Lund, Sweden, looked at melatonin, which regulates sleep-wake cycles and is an indicator of circadian function. Melatonin levels typically cycle up and down slowly, once per day, peaking in the evening hours. To be able to observe this cycling, they measured melatonin levels in 35 people, every half hour for a full day. The group was made up of 20 people with PD who were all taking dopamine medications (12 of whom had reported experiencing excessive daytime sleepiness, or EDS) and 15 people without PD.

Results

People with Parkinson’s disease exhibited normal cycling of their melatonin levels; however, their melatonin levels were significantly lower (about a third as high) as levels in healthy people. In other words, instead of reaching a tall peak, their melatonin levels climbed a little hill.

The people with Parkinson’s who also experienced excessive daytime sleepiness had even lower melatonin levels than the typical person with Parkinson’s – melatonin levels were half of those in people with PD but no EDS.

As seen with healthy participants with and without excessive daytime sleepiness, there was no difference in the reported sleep quality of those people with Parkinson’s with or without excessive daytime sleepiness.

What Does It Mean?

This study is the first to carefully measure the fluctuation of melatonin levels in people with PD and to compare those levels to what is seen in healthy people. Investigators achieved this by measuring melatonin every 30 minutes. The study’s results shed light on the extent to which the circadian rhythms are disrupted in PD, linking the severest changes in these rhythms – evidenced by the very low levels of melatonin – with the excessive daytime sleepiness experiences by some of the participants with Parkinson’s. Previous work using different methods had suggested there were no differences in melatonin levels between those with and without PD.

Dr. Videnovic and his colleagues suggest that treatments such as bright-light therapy and melatonin administration, which have been effective in strengthening circadian function and improving sleep in patients with Alzheimer’s disease and bipolar disorder, may also help people with PD. These treatments may also be effective in treating the sleep problems associated with PD and improve quality of life for thousands of people.